hdf5: first stab at hdf5-1.10 support
This CL is a first step towards supporting new features and APIs of HDF5 v1.10.
Right now, anecdotal evidence shows that HDF5 v1.8 is still massively
deployed so support for 1.10 has to be opt-in, by way of an optional
build tag aptly named "hdf5_v1.10"
Updates #16.
Please take a look.